Acetals derived from negatively substituted aldehydes and polynitro- or halonitroethanols

ABSTRACT

Acetals of the formulas CHCl 2  CH(OR) 2 , CCl 3  CH(OR) 2 ,   2  CH(OR) 2 , CF 3  CH(OR) 2 , RO 2  CCH(OR) 2 , and (RO) 2  HCCH(OR) 2  wherein R can be --CH 2  CYZ(NO 2 ), --CH 2  CH 2  CYZ(NO 2 ), --CH 2  C(NO 2 ) 2  CH 3 , --CH 2  C(NO 2 ) 2  CYZ(NO 2 ), --CH 2  C(NO 2 ) 2  CH 2  CYZ(NO 2 ) or --CH 2  C(NO 2 ) 2  C(NO 2 ) 2  CYZ(NO.sub. 2) wherein Y and Z vary independently and can be Cl, F or NO 2 . These acetals are produced by contacting a negatively substituted aldehyde such as CHCl 2  CHO, CCl 3  CHO, CHF 2  CHO, CF 3  CHO, HO 2  CCHO, or OHCCHO with a negatively substitute alcohol of the formula ROH wherein R is as defined above. Either FSO 3  H, ClSO 3  H, or CHF 2  SO 3  H, or CF 3  SO 3  H is used to catalyze the condensation. The acetals of this invention are useful as explosives.

BACKGROUND OF THE INVENTION

This invention relates generally to acetals and more particularly to acetals containing nitro groups.

Formals and acetals of polynitro - and halonitroethanols (e.g., 2,2,2-trinitroethanol, 2,2,2-fluorodinitroethanol, 2,2-dinitropropanol, 2,2,2-difluoronitroethanol) are of considerable interest as explosive and propellant ingredients. For example, acetals and formals of 2,2-dinitropropanol and 2,2,2-fluorodinitroethanol have been used extensively as energetic plasticizers in various composite propellants and explosives. Special synthesis methods had to be discovered for the preparation of these materials since the extremely low reactivity of the parent alcohols rendered useless the conventional methods for acetal and formal preparation. Thus, U.S. Pat. No. 3,526,667 describes a method for the preparation of formals of nitroalcohols consisting of the condensation with formaldehyde in concentrated sulfuric acid as reaction medium. A method for the preparation of fluorodinitroalkyl acetals, U.S. Pat. No. 3,629,338, uses BF₃ and similar acidic catalysts to effect condensation of acetaldehyde with fluorodinitroalkanols.

However, efforts to employ these methods to prepare acetals and formals derived from aldehydes other than formaldehyde and acetaldehyde have been largely unsuccessful. Especially aldehydes with negative (i.e., electron-withdrawing) substituents were found to be unreactive under the conditions used by these methods. For example, concentrated sulfuric acid fails to catalyze acetal formation between CCl₃ CHO, CF₃ CHO, and HOOCCHO aldehydes and (NO₂)₂ FCCH₂ OH.

SUMMARY OF THE INVENTION

Accordingly, one objective of this invention is to provide novel acetals having high explosive energy content.

Another object of this invention is to provide novel explosive acetals which are thermally stable.

A further object of this invention is to provide novel acetals which are derived from negatively substituted aldehydes and polynitro or halonitro alcohols.

A still further object of this invention is to provide a process for reacting polynitro and halonitro alcohols with negatively substituted aldehydes to form high energy acetals.

These and other objects of this invention are accomplished by providing compounds of the formula CHCl₂ CH(OR)₂, CCl₃ CH(OR)₂, CHF₂ CH(OR)₂, CF₃ CH(OR)₂, RO₂ CCH(OR)₂, and (RO)₂ CHCH(OR)₂ wherein R is selected from the group consisting of --CH₂ CYZ(NO₂), --CH₂ CH₂ CYZ(NO₂), --CH₂ C(NO₂)₂ CH₃, --CH₂ C(NO₂)₂ CYZ(NO₂), --CH₂ C(NO₂)₂ CH₂ CYZ(NO₂), and --CH₂ C(NO₂)₂ C(NO₂)₂ CYZ(NO₂), wherein Y and Z vary independently and are selected from the group consisting of Cl, F, and NO₂. These acetals are prepared by using sulfonic acids selected from the group consisting of CHF₂ SO₃ H, CF₃ SO₃ H, FSO₃ H, and ClSO₃ H to catalyze condensation reactions between polynitro or halonitro alcohols and negatively substituted aldehydes.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The synthesis of compounds of this invention can be shown by the following general reactions:

(I) CHCl₂ CHO + 2ROH → CHCl₂ CH(OR)₂ + H₂ O

(ii) ccl₃ CHO + 2ROH → CCl₃ CH(OR)₂ + H₂ O

(iii) chf₂ cho + 2roh → chf₂ ch(or)₂ + h₂ o

(iv) cf₃ cho + 2roh → cf₃ ch(or)₂ + h₂ o

(v) ho₂ ccho + 3roh → ro₂ cch(or)₂ + 2h₂ o

(vi) ohccho + 4roh → (ro)₂ chch(or)₂ + 2h₂ o

wherein R is selected from the group consisting of --CH₂ CYZ(NO₂), --CH₂ CH₂ CYZ(NO₂), --CH₂ C(NO₂)₂ CH₃, --CH₂ C(NO₂)₂ CYZ(NO₂), --CH₂ C(NO₂)₂ CH₂ CYZ(NO₂), and --CH₂ C(NO₂)₂ C(NO₂)₂ CYZ(NO₂), wherein Y and Z vary independently and are selected from the group consisting of Cl, F, and NO₂.

Equations (I), (II), (III), and (IV) show the general reaction of halo substituted acetaldehydes with polynitro and halonitro alcohols to form acetals. Two molecules of alcohol of the formula ROH react with one molecule of aldehyde selected from the group consisting of CHCl₂ CHO, CCl₃ CHO, CHF₂ CHO, and CF₃ CHO to form an acetal selected from the group consisting of CHCl₂ CH(OR)₂, CCl₃ CH(OR)₂, CHF₂ CH(OR)₂, and CF₃ CH(OR)₂ respectively wherein R is as defined above. Preferred are acetals selected from the group consisting of CHCl₂ CH[OCH₂ C(NO₂)₂ CH₃ ]₂, CCl₃ CH[OCH₂ C(NO₂)₂ CH₃ ]₂, CHF₂ CH[OCH₂ C(NO₂)₂ CH₃ ]₂, CF₃ CH[OCH₂ C(NO₂)₂ CH₃ ]₂ CHCl₂ CH[OCH₂ CYZ(NO₂)]₂, CCl₃ CH[OCH₂ CYZ(NO₂)]₂, CHF₂ CH[OCH₂ CYZ(NO₂)]₂, and CF₃ CH[OCH₂ CYZ(NO₂)]₂, wherein Y and Z vary independently and are selected from the group consisting of Cl, F, and NO₂. More preferred are compounds selected from the group consisting of CCl₃ CH[OCH₂ C(NO₂)₃ ]₂, CF₃ CH[OCH₂ C(NO₂)₃ ]₂, CCl₃ CH[OCH₂ CF(NO₂)₂ ]₂, and CF₃ CH[OCH₂ CF(NO₂)₂ ]₂, with CCl₃ CH[OCH₂ CF(NO₂).sub. 2 ]₂, and CF₃ CH[OCH₂ CF(NO₂)₂ ]₂ being the most preferred.

Equation (V) shows the reaction of one molecule of glyoxylic acid HO₂ CCHO, with 3 molecules of polynitro and halonitro alcohols to form a compound containing both an acetal and an ester group, RO₂ CCH(OR)₂, wherein R is selected from the group consisting of --CH₂ CYZ(NO₂), --CH₂ CH₂ CYZ(NO₂), --CH₂ C(NO₂)₂ CH₃, --CH₂ C(NO₂)₂ CYZ(NO₂), --CH₂ C(NO₂)₂ CH₂ CYZ(NO₂), and --CH₂ C(NO₂)₂ C(NO₂)₂ CYZ(NO₂), wherein Y and Z vary independently and are selected from the group consisting of Cl, F, and NO₂. Preferred are compounds selected from the group consisting of CH₃ C(NO₂)₂ CH₂ O₂ CCH[OCH₂ C(NO₂)₂ CH₃ ]₂, (NO₂)₃ CCH₂ O₂ CCH[OCH₂ C(NO₂)₃ ]₂, (NO₂)₂ FCCH₂ O₂ CCH[OCH₂ CF(NO₂)₂ ].sub. 2, and (NO₂)F₂ CCH₂ O₂ CH[OCH₂ CF(NO₂)₂ ]₂, with (NO₂)₂ FCCH₂ O₂ CCH[OCH₂ CF(NO₂)₂ ]₂ being the most preferred.

Finally equation (VI) shows the reaction of one molecule of glyoxal, OHCCHO, with 4 molecules of polynitro or halonitro alcohol to form a diacetal of the formula (RO)₂ CHCH(OR)₂, wherein R is selected from the group consisting --CH₂ CYZ(NO₂), --CH₂ CH₂ CYZ(NO₂), --CH₂ C(NO₂)₂ CH₃, --CH₂ C(NO₂)₂ CYZ(NO₂), --CH₂ C(NO₂)CH₂ CYZ(NO₂), and --CH₂ C(NO₂)₂ C(NO₂)₂ CYZ(NO₂), wherein Y and Z are selected from the group consisting of Cl, F, and NO₂. Preferred are compounds selected from the group consisting of [CH₃ C(NO₂)₂ CH₂ O]₂ CHCH[OCH₂ C(NO₂)₂ CH₃ ]₂, [(NO₂)₃ CCH₂ O]₂ CHCH[OCH₂ C(NO₃)₃ ]₂, [(NO₂)₂ FCCH₂ O]₂ CHCH[OCH₂ CF(NO₂)₂ ]₂, and [(NO₂ )F₂ CCH₂ O]₂ CHCH[OCH₂ CF₂ (NO₂)], with [(NO₂)₂ FCCH₂ O]₂ CHCH[OCH₂ CF(NO₂)₂ ]₂ being the most preferred.

Most critical to the synthesis of the compounds of the present invention is the selection of a catalyst. Prior art catalysts such as boron trifluride or concentrated sulfuric acid fail to promote the condensation reactions of the present invention. However, it has been found that acids such as FSO₃ H, CHF₂ SO₃ H, CF₃ SO₃ H, and ClSO₃ H will catalyze the synthesis reactions of the present invention (i.e., equations (I) through (VI)). FSO₃ H, CHF₂ SO₃ H, and CF₃ SO₃ H are the preferred catalysts with CF₃ SO₃ H being the most preferred catalyst. Other acids of comparable strength may be used. For example, a perfluoroalkylsulfonic acid having from 2 to 5 carbon atoms may be used in place of trifluoromethanesulfonic acid as the catalyst.

The reactions should be conducted in a solvent which is inert to the reactants, products, and catalyst. Methylene chloride, chloroform, carbon tetrachloride, ethylene chloride and similar solvents are suitable.

The present reactions may be run at from 0° to 45°C with 15° to 35° being preferred.

It will be apparent that the method of synthesis of the present invention may be applied to produce cyclic acetals and polymeric acetals by using the appropriate polynitro halonitro polyols.

To more clearly illustrate this invention, the following examples are presented. It should be understood, however, that these examples are presented merely as a means of illustration and are not intended to limit the scope of the invention in any way.

EXAMPLE I Bis(2,2,2-fluorodinitroethyl)trichloracetal

10 ml. of anhydrous trifluoromethanesulfonic acid was added dropwise to an ice cooled mixture of 5.6g CCl₃ CHO and 6.2g 2,2,2-fluorodinitroethanol, CF(NO₂)₂ CH₂ OH. The initially homogeneous mixture soon became turbid. The mixture was then stirred for 24 hours at ambient temperature. Next, the mixture was poured over crushed ice and the crude product was extracted into methylene chloride. Removal of low-boilers in vacuo left 9g of the crude product containing several minor (total less than 5%) impurities. A pure sample was obtained by running a methylene chloride solution of the crude product through a column of Silica (G. F. Smith, Columbus, Ohio), the impurities being eluted long before the main product, which was obtained as a colorless oil.

Analysis: Calculated for C₆ H₅ F₂ Cl₃ N₄ O₁₀ : C, 16.47; H, 1.15; Cl, 24.31: F, 8.69; N, 12.81; m.w. 437.48. Found C, 16.3; H, 1.3; Cl, 24.4; F, 8.8; N. 12.5; m.w. (McCN), 438.

NMR (CDCl₃). δ 4.94 d (J_(HF) 18 cps); δ 5.08 s; area ratio 4:1

EXAMPLE II Bis(2,2,2-fluorodinitroethyl)trifluoroacetal

A solution of 5.75g of fluoral hydrate, CF₃ CH(OH)₂, and 16.25g of 2,2,2-fluorodinitroethanol, CF(NO₂)₂ CH₂ OH, in 50 ml of trifluoro methanesulfonic acid was stirred at ambient temperature for 24 hours, then warmed to 40° and stirred an additional 65 hours. The reaction mixture was poured over crushed ice, the product extracted with methylene chloride, and the extracts were washed with 0.1N NaOH solution until the aqueous phase remained colorless. Removing the solvent left 12g of a light brown oil whose main component was Bis(2,2,2-fluorodinitroethyl)trifluoroacetal.

A pure sample of the acetal was obtained by repeated chromatography on Silica (G. F. Smith, Columbus, Ohio) with methylene chloride/hexane (1.5:3.5 to 1.75:3.25) as eluant; progress of the purification was followed by gas chromatographic analysis. The solvents were removed by maintaining the solution at 0.5 mm/40°C for several hours. The purified Bis(2,2,2-fluorodinitroethyl)trifluoroacetal was a light amber oil, M.P. -1° to 0°C.

Analysis: Calculated for C₆ H₅ F₅ N₄ O₁₀ ; C, 18.57; H, 1.30; F, 24.48; N, 14.44; m.w., 388.13, Found: C, 19.0, H, 1.2; F, 25.2; N, 14.7; m. w. (MeCN), 388.

NMR (CDCl₃): δ 4.83 d (J_(HF) 15 cps); δ 5.08 q (J_(HF) 4 cps); areas ca. 4:1.

EXAMPLE III 2,2,2-Fluorodinitroethyl bis(2,2,2-fluorodinitroethyxy)acetate

A mixture of 4.65g of 2,2,2-fluorodinitroethanol, 0.75g of anhydrous glyoxylic acid, HOOCCHO, and 5 ml of trifluoromethanesulfonic acid was stirred at ambient temperature of 24 hours. After pouring over crushed ice, the product was extracted into methylene chloride, the extracts were dried and the solvent removed to give 5.1g of 2,2,2-fluorodinitroethyl bis(2,2,2,-fluorodinitroethoxy)acetate, a colorless oil. Filtration in methylene chloride solution through a column of Silica (G. F. Smith, Columbus, Ohio) removed 2,2,2-fluorodinitroethanol and other minor impurities, yielding a product of analytic purity M.P. 34.5°-35.5 °C.

Analysis: Calculated for C₈ H₇ F₃ N₆ O₁₆ : C, 19.21; H, 1.41; F, 11.40; m.w., 500.18. Found: C, 19.2; H, 1.4; F, 11.0; m. w. (MeCN), 493.

NMR (CDCl₃): two overlapping AB quartets centered near δ 4.75 and δ 4.92 (acetal CH₂ protons); δ 5.29 d (J_(HF) 16 cps; ester CH₂ protons) δ 5.30 s.

EXAMPLE IV 2,2,2-Trinitroethyl bix(2,2,2-trinitroethoxy)acetate

Trifluoromethanesulfonic acid, 7.5 ml, was added with cooling to a mixture of 5.43g trinitroethanol and 0.75g glyoxylic acid. After stirring for 24 hours at ambient temperature, the mixture was poured over crushed ice, the precipitate filtered off and washed with water. Obtained was 4.6g (79%) crude product; mp after recrystallization from ethylene chloride/carbon tetrachloride 100°-101.5°C.

Analysis: Calculated for C₈ H₇ N₉ O₂₂ : C, 16.53; H. 1.21; N, 21.69; m. w. 581.20. Found C, 16.6; H, 1.2; N, 21.3; m. w. (MeCN), 542.

NMR (CDCl₃): δ 5.07, 5.10 two overlapping singlets (acetal CH₂ protons); δ 5.51 s (ester CH₂); δ 5.53 s (CH); area ratio of signals near 5.1 to signals near 5.5. ca. 4:3.

EXAMPLE V 2,2,2-Difluoronitroethyl bis(2,2,2-difluoronitroethoxy)acetate

Trifluoromethanesulfonic acid, 10 ml, was added with ice-cooling and vigorous stirring to a mixture of 7.7g 2,2,2-difluoronitroethanol and 1.5g glyoxylic acid. Next, the mixture was stirred for 24 hours at ambient temperature. The mixture was then poured over crushed ice and the product extracted into methylene chloride. The extracts were washed with water, dried over magnesium sulfate and freed from solvent in vacuo to give 8.5g crude dialkoxy ester. The product was purified by filtration, in methylene chloride-hexane solution, through a column of Silica to give a material of 98+% purity(gas chromotographic analysis); mp -3° to -2°C, d(20°C) 1.63.

EXAMPLE VI Tetrakis(2,2,2-fluorodinitroethoxy)ethane

To a mixture of 6.2g of 2,2,2-fluorodinitroethanol and 0.58g glyoxal trimer was added with ice-cooling 7.5 ml trifluoromethanesulfonic acid. The mixture was stirred 50 hours at ambient temperature and poured over crushed ice. The precipitate was filtered off and dried to give 3.25g (50.6% yield) of crude product. The product was purified by recrystallization from ethylene chloride/carbon tetrachloride. The solid product had a melting point of 106.5°-107.5 °C.

Analysis: Calculated for C₁₀ H₁₀ F₄ N₈ O₂₀ : C, 18.82; H, 1.58; N, 17.56; F, 11.91; m. w. 638.24. Found: C, 19.2; H, 1.6; N, 17.4; F, 11.7; m. w. (MeCN, MEK), 674, 618.

NRM (CDCl₃ /acetone-d): δ 4.84 (J_(HF) 16 cps); δ 4.97 s; areas ca 4:1.

EXAMPLE VII Tetrakis(2,2,2-trinitroethoxy)ethane

A mixture of 1.16g glyoxal trimer, 14.50g 2,2,2-trinitroethanol and 15 ml trifluoromethanesulfonic acid was stirred at ambient temperature for 48 hours, then poured over crushed ice, the solid filtered off and allowed to dry in air to give 6.25g crude product. The main product is separated from an impurity by fractional crystallization from carbon tetrachloride, acetonitrile or ethylene dichloride, where the by-product is considerably less soluble; mp (from ethylene chloride) 167°-168°C (dec.).

Analysis: Calculated for C₁₀ H₁₀ N₁₂ O₂₈ : C, 16.09; H, 1.35; N, 22.52 m. w., 746.26. Found: C, 16.4; H, 1.4; N, 22.2; m. w., (MeCN), 737.

NMR (CD₃ CN-C₆ D₆): δ 5.05 s; δ 5.12, 5.14 two overlapping singlets; areas ca. 1:4. 

What is claimed as new and desired to be secured by Letters Patent of the United States is:
 1. A compound of the formula (RO)₂ CHCH(OR)₂ wherein R is selected from the group consisting of --CH₂ CYZ(NO₂) and --CH₂ C(NO₂)₂ CH₃, wherein Y and Z vary independently and are selected from the group consisting of Cl, F, and NO₂.
 2. A compound according to claim 1 which is selected from the group consisting of [(NO₂)₃ CCH₂ O]₂ CHCH[OCH₂ C(NO₂)₃ ]₂ and [(NO₂)₂ FCCH₂ O]₂ CHCH[OCH₂ CF(NO₂)₂ ]₂.
 3. A compound according to claim 2 which is [(NO₂)₂ FCCH₂ O]₂ CHCH [OCH₂ CF(NO₂)₂ ]₂.
 4. A compound according to claim 1 which is [(NO₂)F₂ CCH₂ O--₂ CH₂ CH₂ --OCH₂ CF₂ (NO₂)]₂. 